CVE-2026-4686Network attack vector

Service interruption via Canvas2D boundary handling

Published Mar 24, 2026 · Updated Mar 24, 2026

Incorrect boundary handling in Mozilla Canvas2D allows remote attackers to interrupt affected Firefox and Thunderbird releases. Mozilla identifies the Graphics: Canvas2D component but has not published the affected function, the mishandled boundary, or the triggering input operation. Reachability requires Canvas2D content processing; Thunderbird blocks scripting in ordinary email reading, so exposure there is limited to browser or browser-like contexts.

CVSS severity7.5
High
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect boundary handling in Mozilla Canvas2D allows remote attackers to interrupt affected Firefox and Thunderbird releases. Mozilla identifies the Graphics: Canvas2D component but has not published the affected function, the mishandled boundary, or the triggering input operation. Reachability requires Canvas2D content processing; Thunderbird blocks scripting in ordinary email reading, so exposure there is limited to browser or browser-like contexts.

The record

CVE
CVE-2026-4686
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-787, CWE-754, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <149

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <149
Mozilla · Thunderbirdversion=unspecified <140.9; version=unspecified <149
Mozilla · Firefox ESRversion=unspecified <115.34; version=unspecified <140.9

Published CVSS scores

8.8SUSECVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-754Improper Check for Unusual or Exceptional Conditions
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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